NewLogicCircuitswithaBetterSwitchTraditionaldigitalCMOShasoperatedbetweenONandOFFstates,asexplainedinFigure12.TheexcellentIonandIoffcharacteristicsofthemulti-gatedevicesallowfuturescalingoftraditionalcircuitsforafewgenerations.Eventhisisnotsufficientforcertainlow-powerapplicationssuchaspacemakers,hearingaids,andotherself-poweredlogicdevices.Whilesub-thresholdlogichasbeenproposedasalow-powercircuit
New Logic Circuits with a Better Switch
Traditi
onal digital
CMOSh
asoperated between ON and OFF states, as explained in Figure 12. The excellent Ion and Ioff characteristics of the multi-gate devices allow future scaling of traditional circuits for a few generations. Even this is not sufficient for certain low-
powerapplications such as pacemakers, hearing aids, and other self-powered logic devices. While sub-threshold logic has been proposed as a low-power circuit alternative, it has not been widely used, due in part to the limitations of single gate devices. Multi-gate devices, with their steep turn on characteristics and extremely low leakage characteristics, promise to be ideal to make these systems practical [
16].
New Analog Circuits
CanUse Multiple Independent Gates
While digital CMOS logic leads the process technology roadmap for computing applications, the communications or
RFapplications have a substantial mix of analog components that are integrated into the CMOS logic or as standalone products. The double-gate device architecture allows better scaling of these analog applications and new functions that were not possible with single gate transistors. Just as in CMOS logic, the fundamental switch is improved by the double-gate architecture for analog applications.
The double-gate architecture offers better gain and can be used as a better mixer, amplifier or VCO.
Beyond the Transistor
Rotated substrates or junction engineering are examples of developments to deliver the best drive currents while minimizing the off-state leakages. SOI technology brings higher speed at lower power through reduced capacitances and improved performance at a given voltage.
High-k Metal-Insulator-Metal (
MIM) capacitor is a decoupling capacitance technology that helps voltage supply integrity. And also, the low-k and ultra-low-k interconnect insulators reduce capacitance and thereby drive down the chip-level power.
